This invention aims to improve the original preceding application case in the digit of display position and the sensing method. In the preceding case, the digital display is positioned at a fixed point on the apparatus. If it is too high, a short person has to raise his (or her) head to read the digits displayed; if it is too low, a tall person has to lower his head to read the digits. Further, said motion of raising or lowering one's head is liable to cause some errors in measuring the body height. The best position of said digital display for obtaining accurate height measurement is within the range higher no more than that of the forehead of an average person. The digital display means in the preceding case generates signal by means of the metal contact point being touched with the sliding PCB: the touch between said metal contact point and said PCB has to be accurate and smooth. When assembling them, special care must be taken on their positions without any error; otherwise, bad contact or tear and wear may be resulted to cause the whole expensive machine to become unserviceable.